Disclosed herein is a process for preparing digitally printed scattering surface effects using ink jet ink and non-ink jettable particles. More particularly disclosed is a method for creating controlled scattering effects comprising (a) disposing at least one curable ink layer onto a substrate in an imagewise fashion or in a continuous film fashion; (b) applying a first cure to partially cure the ink layer (a); (c) disposing at least one scattering material onto the ink layer (a); and (d) applying a second cure to fully cure the ink layer (a); wherein the first cure and the second cure are applied in a manner to control the disposition of the scattering material on top of and penetration into the curable ink layer to control surface and subsurface scattering properties.
Also disclosed is a printing method comprising (a) ink jetting at least one curable ink layer onto a substrate in an imagewise fashion or in a continuous film fashion; (b) applying a first cure to partially cure the ink layer (a); (c) disposing at least one scattering material onto the ink layer (a); and (d) applying a second cure to fully cure the layer (a).
Ink jet inks which contain a dye or pigment, a solvent system, which may be aqueous or non-aqueous and may include a combination of solvents or a single solvent, and various other components are known. These other components may be included to address specific problems relating to ink performance, such as flow characteristics, the ink drying out over time as it sits in the cartridge or when it is deposited through the nozzle during printing, particulate matter in the ink settling out of solution over time, and the like.
A current need is for improved ink compositions suitable for drop based printing. For example, there is a need for improved ink compositions for drop based printing such as tonejet printing which pulls drops with charged particles from the liquid.
Another current need is the ability to digitally print ink jet inks with high concentrations of particles that are too large to jet.
Ink jetting devices are known in the art, and thus extensive description of such devices is not required herein. As described in U.S. Pat. No. 6,547,380, incorporated herein by reference, ink jet printing systems generally are of two types: continuous stream and drop-on-demand. In continuous stream ink jet systems, ink is emitted in a continuous stream under pressure through at least one orifice or nozzle. The stream is perturbed, causing it to break up into droplets at a fixed distance from the orifice. At the break-up point, the droplets are charged in accordance with digital data signals and passed through an electrostatic field that adjusts the trajectory of each droplet in order to direct it to a gutter for recirculation or a specific location on a recording medium. In drop-on-demand systems, a droplet is expelled from an orifice directly to a position on a recording medium in accordance with digital data signals. A droplet is not formed or expelled unless it is to be placed on the recording medium.
There are at least four types of drop-on-demand ink jet systems. One type of drop-on-demand system is a piezoelectric device that has as its major components an ink filled channel or passageway having a nozzle on one end and a piezoelectric transducer near the other end to produce pressure pulses. Another type of drop-on-demand system is known as acoustic ink printing. As is known, an acoustic beam exerts a radiation pressure against objects upon which it impinges. Thus, when an acoustic beam impinges on a free surface (i.e., liquid/air interface) of a pool of liquid from beneath, the radiation pressure which it exerts against the surface of the pool may reach a sufficiently high level to release individual droplets of liquid from the pool, despite the restraining force of surface tension. Focusing the beam on or near the surface of the pool intensifies the radiation pressure it exerts for a given amount of input power. Still another type of drop-on-demand system is known as thermal ink jet, or bubble jet, and produces high velocity droplets. The major components of this type of drop-on-demand system are an ink filled channel having a nozzle on one end and a heat generating resistor near the nozzle. Printing signals representing digital information originate an electric current pulse in a resistive layer within each ink passageway near the orifice or nozzle, causing the ink vehicle (usually water) in the immediate vicinity to vaporize almost instantaneously and create a bubble. The ink at the orifice is forced out as a propelled droplet as the bubble expands. Still another type of drop-on-demand system is tonejet printing comprising an electrostatic drop-on-demand deposition technology. The tonejet process consists of electrostatic concentration and ejection of particles from a fluid. The tonejet print head enables an electric field to be applied to the ink. The tonejet ink comprises electrically charged conventional pigments in a non-conductive liquid. In the tonejet print head, an electric force is applied directly to the charged ink particles. The longer the electric pulse is applied, the more ink is ejected. See, for example, U.S. Pat. No. 6,260,954, which is hereby incorporated by reference herein in its entirety, which describes in the Abstract thereof a method and apparatus for the generation of agglomerations of particulate material in a liquid. Agglomerations are built up at a point under the effect of an electric field and ejected by electrostatic means. The size of the agglomeration is dependent upon the strength of the electric filed, point geometry, the nature of the liquid, and the nature of the particles. Agglomerations of particles in the range of from 1 to 500 microns are produced. The invention is useful for non-impact printing and other applications where delivery of agglomerations of particles is useful such as in inhalable pharmaceuticals.
In a typical design of a piezoelectric ink jet device utilizing phase change inks printing directly on a substrate or on an intermediate transfer member, such as the one described in U.S. Pat. No. 5,372,852, incorporated herein by reference, the image is applied by jetting appropriately colored inks during four to eighteen rotations (incremental movements) of a substrate (an image receiving member or intermediate transfer member) with respect to the ink jetting head, i.e., there is a small translation of the printhead with respect to the substrate in between each rotation. This approach simplifies the printhead design, and the small movements ensure good droplet registration. At the jet operating temperature, droplets of liquid ink are ejected from the printing device and, when the ink droplets contact the surface of the recording substrate, either directly or via an intermediate heated transfer belt or drum, they quickly solidify to form a predetermined pattern of solidified ink drops.
Hot melt inks typically used with ink jet printers have a wax based ink vehicle, e.g., a crystalline wax. Such solid ink jet inks provide vivid color images. In typical systems, these crystalline wax inks partially cool on an intermediate transfer member and are then pressed into the image receiving medium such as paper. Transfuse spreads the image droplet, providing a richer color and lower pile height. The low flow of the solid ink also prevents bleedthrough on the paper.
In these systems, the crystalline wax inks are jetted onto a transfer member, for example, an aluminum drum, at temperatures of approximately 100° C. to about 130° C. The wax based inks are heated to such high temperatures to decrease their viscosity for efficient and proper jetting onto the transfer member. The transfer member is at approximately 60° C., so that the wax will cool sufficiently to solidify or crystallize. As the transfer member rolls over the recording medium, e.g., paper, the image comprised of wax based ink is pressed into the paper.
Piezoelectric ink jet techniques are known, and offer a reliable and cost effective means of applying digital images. However, ink jet inks and substances capable of being deposited on a substrate through ink jetting currently are required to have a small particle size and a low solid particle content. Large particles and high loadings make it difficult to combine such solid particles to inkjet technology, especially solvent free ink jet applications, as the particle size impedes normal function of the jetting nozzles and other equipment by, for example, clogging or requiring that the nozzle diameter be so large as to prevent accurate printing.
U.S. Pat. No. 8,123,347, which is hereby incorporated by reference herein in its entirety, describes in the Abstract thereof methods of using inks with gellants that can form a gel state, as receivers for particle materials. The inks are liquid when jetted, but quickly enter a tacky-semi-solid/gel state when cooled below ink gel temperature on a substrate and prior to curing. Dry powders and solid particulate substances of various are then applied to the jetted inks and locked in place when the ink is cured. U.S. Pat. No. 8,123,347 in particular describes the curing of magnetite powders that have been deposited onto ultraviolet curable ink.
Highly pigmented inks with large particles can exhibit desirable high color saturations with thin, and therefore, less expensive, and mechanically more robust ink layers. Concentrated particle inks are also capable of exhibiting controlled properties to exhibit enhanced appearance ranging from metal specular, high gloss, low gloss, and flat appearances. Inclusion of large particulates such as glitters and flakes can further potentially enhance optical appearances. The ability to incorporate particulates with unique chemical, biological, physical, and electrical properties is also highly desirable. Also desirable would be the ability to effect continuous control of optical properties on non-planar surfaces for three-dimensional printed objects as well as the ability to create novel scattering and/or absorbing effects on two-dimensional printed surfaces. However, due to the size and shape requirements for light scattering materials, these particles are too large for ink jet printing.
Currently available processes are suitable for their intended purposes. However a need remains for a process and suitable ink jet inks to enable application of unjettable pigments in a controlled fashion using digital marking technologies.
The appropriate components and process aspects of the each of the foregoing U.S. Patents and Patent Publications may be selected for the present disclosure in embodiments thereof. Further, throughout this application, various publications, patents, and published patent applications are referred to by an identifying citation. The disclosures of the publications, patents, and published patent applications referenced in this application are hereby incorporated by reference into the present disclosure to more fully describe the state of the art to which this invention pertains.